Latency reduction is one of the considerations in a GSM/EDGE radio access network (GERAN). Two techniques have been proposed for the latency reduction: reduced transmission time interval (RTTI) and fast acknowledgement/non-acknowledgement (ACK/NACK) reporting (FANR).
Under current GERAN protocols, the network may obtain feedback data, (i.e., ACK/NACK of downlink data packets), from the mobile station through polling. The polling is indicated by an evolved general packet radio service (EGPRS) supplementary polling (ES/P) field. Two (2) ES/P bits indicate whether a relative reserved block period (RRBP) field is valid or not and what fields the next uplink control block shall contain.
FIGS. 1-3 show conventional EGPRS downlink radio link control/medium access control (RLC/MAC) header types 1, 2, and 3, respectively. Both the ES/P field and the RRBP field are present in all three RLC/MAC header types. Table 1 shows the meaning of the conventional 2-bit ES/P field.
TABLE 1bits54ES/P00RRBP field is not valid (no Polling)01RRBP field is valid - Extended Ack/Nack bitmap typeFPB10RRBP field is valid - Piggy-backed Ack/Nack bitmap typeFPB11RRBP field is valid - Extended Ack/Nack bitmap typeNPB, measurement report included
Conventionally, an ACK/NACK report is sent in an explicit message, also referred to as an RLC/MAC control block. The ACK/NACK report is addressed to a particular radio resource, called a Temporary Block Flow (TBF). A TBF is a temporal connection between a mobile station and a network to support a uni-directional transfer of data. A TBF is temporary and is maintained only for the duration of the data transfer.
It has been proposed that the ACK/NACK feedback for a certain TBF be “piggybacked” on an RLC/MAC data block that may be addressed to another TBF. The field that carries this ACK/NACK feedback is referred to as “piggybacked ACK/NACK (PAN) field”. The presence or absence of the PAN field in the RLC/MAC data block is indicated by a PAN indicator (PANI).
In order to send the PANI, an extra bit may be included in a downlink data packet header as shown in FIGS. 1-3. However, currently there is no available space in the downlink data packet header. It has been proposed to split the conventional 2-bit RRBP field such that one bit is used for the RRBP field and the other bit is used for the PANI. Tables 2 and 3 show the meaning of the 1-bit RRBP field and 1-bit PANI field.
TABLE 2BitFull-rate PDCH uplink block with TDMA frame number0(N + 8 or N + 9) mod 27156481(N + 13) mod 2715648
TABLE 3bitPANI0A PAN field is not included1A PAN field is included
In accordance with this proposal, the header size remains the same. However, there is redundancy in bit combinations. If the ES/P bits are “00”, (i.e., when there is no polling request), the combinations of the RRBP bit and the PANI bit include wastage of three (3) combinations. Therefore, it would be desirable to provide a scheme for more efficient signaling of a PANI, an RRBP, and a polling indicator.